DECIGO/BBO as a probe to constrain alternative theories of gravity

Kent Yagi; Takahiro Tanaka

doi:10.1143/PTP.123.1069

paper

DECIGO/BBO as a probe to constrain alternative theories of gravity

arXiv:0908.3283 · doi:10.1143/PTP.123.1069

Abstract

We calculate how strongly one can constrain the alternative theories of gravity with deci-Hz gravitational wave interferometers such as DECIGO and BBO. Here we discuss Brans-Dicke theory and massive graviton theories as typical examples. We consider the inspiral of compact binaries composed of a neutron star (NS) and an intermediate mass black hole (IMBH) for Brans-Dicke (BD) theory and those composed of a super massive black hole (SMBH) and a black hole (SMBH) for massive graviton theories. Using the restricted 2PN waveforms including spin effects and taking the spin precession into account, we perform the Monte Carlo simulations of $1 0^{4}$ binaries to estimate the determination accuracy of binary parameters including the Brans-Dicke parameter $ω_{BD}$ and the graviton Compton length $λ_{g}$ . Assuming a $(1.4, 10) M_{⊙}$ NS/BH binary of SNR= $200$ , the constraint on $ω_{BD}$ is obtained as $ω_{BD} > 2.32 \times 1 0^{6}$ , which is 300 times stronger than the estimated constraint from LISA observation. Furthermore, we find that, due to the expected large merger rate of NS/BH binaries of $O (1 0^{4})$ yr $^{- 1}$ , a statistical analysis yields $ω_{BD} > 3.77 \times 1 0^{8}$ , which is 4 orders of magnitude stronger than the current strongest bound obtained from the solar system experiment. For massive graviton theories, assuming a $(1 0^{6}, 1 0^{5}) M_{⊙}$ BH/BH binary at 3Gpc, one can put a constraint $λ_{g} > 3.35 \times 1 0^{20}$ cm, on average. This is three orders of magnitude stronger than the one obtained from the solar system experiment. From these results, it is understood that DECIGO/BBO is a very powerful tool for constraining alternative theories of gravity, too.

4 pages, 3 figures; Accepted to Prog. Theor. Phys. Letters; Many interpretations and some references have been added; Some Coding errors being corrected and the final constraints came out stronger

DECIGO/BBO as a probe to constrain alternative theories of gravity

Abstract

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